Eosinophils have been implicated in the pathogenesis of a wide variety of inflammatory disease states including allergic disorders associated with hypersensitivity reactions in the lung tissue (Butterfield et al., In: Immunopharmacology of Eosinophils, H. Smith and R. Cook, Eds., p.151-192, Academic Press, London (1993)). A notable example is asthma, a disease characterized by reversible obstruction of the airways leading to non-specific bronchial hyperresponsiveness. This in turn is dependent upon the generation of a chronic inflammatory reaction at the level of the bronchial mucosa and a characteristic infiltration by macrophages, lymphocytes and eosinophils. The eosinophil appears to play a central role in initiating the mucosal damage typical of the disease (Corrigan et al., Immunol. Today, 13:501-507 (1992)). Increased numbers of activated eosinophils have been reported in the circulation, bronchial secretions and lung parenchyma of patients with chronic asthma, and the severity of the disease, as measured by a variety of lung function tests, correlates with blood eosinophil numbers (Griffen et al., J. Aller. Clin. Immunol., 67:548-557 (1991)). Increased numbers of eosinophils, often in the process of degranulation, have also been recovered in bronchoalveolar lavage (BAL) fluids of patients undergoing late asthmatic reactions, and reducing eosinophil numbers, usually as a consequence of steroid therapy, is associated with improvements in clinical symptoms (Bousquet et al., N. Eng. J. Med., 323:1033-1039 (1990)).
Interleukin 5 (IL-5) is a homodimeric glycoprotein produced predominantly by activated CD4+ T lymphocytes. In man, IL-5 is largely responsible for controlling the growth and differentiation of eosinophils. Elevated levels of IL-5 are detected in the bronchoalveolar lavage washings of asthmatics (Motojima et al., Allergy, 48:98 (1993)). Mice which are transgenic for IL-5 show a marked eosinophilia in peripheral blood and tissues in the absence of antigenic stimulation (Dent et al., J. Exp. Med., 172:1425 (1990)) and anti-murine IL-5 monoclonal antibodies have been shown to have an effect in reducing eosinophilia in the blood and tissues of mice (Hitoshi et al., Int. Immunol., 3:135 (1991)) as well as the eosinophilia associated with parasite infection and allergen challenge in experimental animals (Coffman et al., Science, 245:308-310 (1989), Sher et al., Proc. Natl. Acad. Sci., 83:61-65 (1990), Chand et al., Eur. J. Pharmacol., 211:121-123 (1992)).
Although corticosteroids are extremely effective in suppressing eosinophil numbers and other inflammatory components of asthma, there are concerns about their side effects in both severe asthmatics and more recently in mild to moderate asthmatics. The only other major anti-inflammatory drug therapies—cromoglycates (cromolyn sodium and nedocromil)—are considerably less effective than corticosteroids and their precise mechanism of action remains unknown.
More recent developments have focused on new inhaled steroids, longer acting bronchodilators and agents acting on novel biochemical or pharmacological targets (e.g., potassium channel activators, leukotriene antagonists, 5-lipoxygenase (5-LO) inhibitors etc.). An ideal drug would be one that combines the efficacy of steroids with the safety associated with cromolyn sodium, yet has increased selectivity and more rapid onset of action. Neutralizing IL-5 antibodies may potentially be useful in relieving eosinophila-related symptoms in man.
Hence there is a need in the art for a high affinity IL-5 antagonist, such as a neutralizing monoclonal antibody to human interleukin 5, which would reduce eosinophil differentiation and proliferation (i.e., accumulation of eosinophils) and thus eosinophil inflammation.